1. Field of the Invention
The present invention relates generally to a door locking-unlocking system for locking and unlocking a door, and particularly to a door closing system for fully closing a side door or a trunk door of a vehicle by forcing a latch of the door closing system to be engaged with a door striker.
2. Related Art
Conventionally, closing a door of a vehicle requires a relatively large force due to reactive force of a weatherstrip attached to the door or lock resistance of the door occurring immediately before the door is fully closed. To overcome this problem, an electrically-driven automatic door closing system is developed. When the door closing system detects that a door is closing and a latch of the door closing system starts being engaged with a door striker, the door closing system fully closes the door by forcing the latch to be engaged with the striker. Generally, the door closing system performs two operations; an unlocking operation for unlocking the door and a latch pulling operation for forcing a latch of the door closing system to be engaged with a door striker when the latch starts being engaged with the striker. Conventionally, the two operations of the door closing system are independently controlled by two electric actuators. Therefore, manufacturing cost and size of the door closing system may be increased. Further, when such a large-sized door closing system is used for the trunk door, a capacity of a trunk may be decreased.
To solve these problems, JP-B2-5-27748 discloses a door closing system having a door lock system, in which the unlocking operation and the latch pulling operation are performed by a single electric actuator.
That is, as shown in FIG. 24A, a door lock system 51 installed in a trunk door of a vehicle has a latch 53 having a recessed portion 53a to be engaged with a striker 52 mounted on the vehicle. The latch 53 is rotatably held by a shaft 54, and is constantly biased in a clockwise direction in FIG. 24A. When the door is closed by a relatively weak force, the latch 53 hits the striker 52, but insufficiently rotates to be positioned as shown in FIG. 24B. At this point, a pawl (ratchet) 55 is latched, thereby restricting further moving of the latch 53. On the other hand, when the door is closed by a relatively large force, the latch 53 hits the striker 52, and sufficiently rotates to be positioned as shown in FIG. 24C, so that the latch 53 is fully engaged with the striker 52. At 25 this point, the pawl 55 is latched, thereby restricting further moving of the latch 53.
As shown in FIG. 23, a door closing system 56 having the door lock system 51 has a single reversible motor 57 as an actuator. When the reversible motor 57 rotates forward, a rotation plate 58 rotates in a clockwise direction in FIG. 23 from a neutral position thereof. As a result, one end of an output member 59 attached to the rotation plate 58 makes contact with an arm 60 and rotates the arm 60, thereby pulling a rod 61. When the rod 61 is pulled, the latch 53 which starts being engaged with the striker 52 is forced to be rotated to be fully engaged with the striker 52.
On the other hand, when the reversible motor 57 is rotated in reverse by a door opening system, the rotation plate 58 rotates in a counterclockwise direction in FIG. 23 from the neutral position. As a result, the other end of the output member 59 hits an arm 62 and rotates the arm 62, thereby pulling a rod 63. When the rod 63 is pulled, the pawl 55 holding the latch 53 to be fully engaged with the striker 52 is rotated so that the latch 53 is released from the striker 52. As a result, the door is unlocked.
However, in this door closing system 56, the rotation plate 58 rotated to pull the rods 61, 63 needs to be disposed to be perpendicular to the latch 53. As a result, the door closing system 56 cannot be reduced in size sufficiently.
Further, the door closing system 56 has two position detection sensors such as microswitches which determine a timing for stopping the actuator when the latch 53 is fully engaged with the striker 52, and a timing for unlocking the door and stopping the actuator at an original initial position. Therefore, the door closing system 56 needs to have an extra space in which the two detection sensors are installed. As a result, reduction in size of the door closing system 56 is further restricted.
Further, in the door closing system 56, when power supply to the actuator is shut off to tentatively stop the actuator and resumes, it can not be determined whether the door closing system 56 has been performing a latch pulling operation for pulling the latch 53 to be fully engaged with the striker 52, or an unlocking operation for unlocking the door before the actuator is stopped, even though the two position detection sensors are used. As a result, the door closing system 56 may erroneously unlock the door when the latch 53 should be pulled to be engaged with the striker 52, or pull the latch 53 when the door should be unlocked.